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gstock
climber
Yosemite Valley
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C Wilmot, I'm not sure where you heard that I offered assurances that the Ahwiyah Point site was "safe", but that is not correct. To the contrary, I had concerns about the block you mentioned, and that is primarily why trail reconstruction didn't occur until three years after the rockfall. Despite what we might wish for, it just isn't possible to predict exactly when and where rockfalls will occur. It is for that reason that I, as a matter of practice, take a more nuanced approach than simply asserting that an area is “safe” (check out my posting history here for examples). I am relieved that nobody was in the vicinity when the block failed in October 2013.
In terms of the rockfall hazard and risk study (available here), the EOS article linked above provides justification for both the study and the resulting actions. Perhaps at some level it is obvious that boulders on the ground indicate rockfall hazard, but making good risk-based decisions requires thorough and quantitative science. “Common sense” is, unfortunately, subjective.
Feel free to call or email me if you’d like to discuss this more.
Greg Stock
Park Geologist
(209) 379-1420
greg_stock@nps.gov
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Captain...or Skully
climber
in the oil patch...Fricken Bakken, that's where
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Yer gonna die fer sure(still).....
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ß Î Ø T Ç H
Boulder climber
extraordinaire
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Concerning rockfall ... Oh, it's "concerning" all right.
That sinking feeling hearing the rattle of bones above you.
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Flip Flop
Trad climber
Truckee, CA
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Greg,
Is there any study of temperatures inside deep fissures in the Valley?
I noticed that rockfall rates rise in October when the temperature swings begin again. Freeze and thaw cycles are pretty impressive forces of nature.
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Reilly
Mountain climber
The Other Monrovia- CA
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It ain't a matter of if, to coin a phrase, is it? Seems to me that all of Curry
is sitting on borrowed time.
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gunsmoke
Mountain climber
Clackamas, Oregon
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Why is the lower canyon (west of Valley floor) active in the winter and the upper canyon relatively inactive in the winter? Could that be related to temperature triggers or other environmental factors, or just a statistical anomaly?
As noted by Greg, the majority of rockfall accidents to climbers are trigged by other climbers. Perhaps the Apron has become one of the safest places to climb. I've been in two rockfall accidents, both triggered by climbers not in my party.
And the map was used to make the decision to move some Curry Village cabins from locations which were fairly high risk.
Were they actually moved, or just removed as part of the unwritten policy to greatly reduce overnight accommodations in the Valley?
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rmuir
Social climber
From the Time Before the Rocks Cooled.
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did John Muir ever trundle?
Of course he did. Along with torching an entire tree in the Meadows just to have a rollickingly big bonfire one night, trundling is something of which he couldn't resist. He just couldn't admit it for fear of being tooled by the Man and getting booted from the Park. That Galen Clark was a real hard nose!
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Tom
Big Wall climber
San Luis Obispo CA
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All that fancy "science" aside, the real reason for the rapid exfoliation of the Valley walls is CAMMING UNITS.
A simple analysis will show that a climber's weight is multiplied, with the springy gadgets pushing out forcefully on flakes and buttresses, causing them to break off and fall.
Whatever happened to simply driving big angles to the tune of bing-bing-bing, or beng-beng-beng, or bong-bong-bong?
As I recall, there was no rockfall back then . . . . .
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Clint Cummins
Trad climber
SF Bay area, CA
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Cams = troll, given that you (should) know there were lots of rockfalls prior to the invention of cams.
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mouse from merced
Trad climber
The finger of fate, my friends, is fickle.
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I've told this before. I was with Millis when the first slide came off in the fall season when we were climbing Stigma--on pitons, very sketchily placed in the squeeziest of thin cracks.
If anything, the Valley is shaking because donini's coming back...
McHale's Navy, good to hear your tale. Loud sh!t, isn't it?
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Impaler
Social climber
Oakland
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Nov 10, 2014 - 01:29pm PT
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Just saw some cool rock fall in the Ribbon falls amphitheater on November 8. It wasn't that much rock, but the location amplified the sound a lot, so it sounded epic. The lower half of the amphitheater was filled with dust for about a minute. Rockfall originated about 1/2 way up the waterfall, which wasn't flowing at the time.
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rbord
Boulder climber
atlanta
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Nov 10, 2014 - 08:15pm PT
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I'm wondering what the other options for rockfall are other than normal geologic processes? Do we know what normal geologic processes are based on 200 years worth of data (or better yet, one lifetime of direct observation)? If we disprove every other hypothesis we can think of, will we have proven to ourselves that it's normal geologic process? I'd say that's a pretty normal human perspective :-) Can we say it's normal geologic process and admit that we don't understand exactly everything that means - every factor involved in every piece of rock falling? It's science dammit!
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Brock
Trad climber
RENO, NV
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Nov 11, 2014 - 07:12am PT
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I've climbed two routes just days prior to major rock fall. One was on The Great Book and the other was on Mr Natural. I remember fine granite dust being on the routes but no major sign of rock fall yet. Are there any warning signs being studied on potential rock fall sites?
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Reilly
Mountain climber
The Other Monrovia- CA
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Nov 11, 2014 - 07:17am PT
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I've been fortunate to have survived two extremely close rockfalls in the Valley but Mother
Nature had nothing to do with either unless she also influences klutzes.
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JEleazarian
Trad climber
Fresno CA
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Nov 11, 2014 - 12:07pm PT
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The first climbing books I read in the mid-1960's said to regard fine dust on the talus as a sure sign of recent, rather than future rockfall. Of course, they also implied that areas of recent rockfall would likely be areas of future rockfall, too.
The Apron seemed particularly immune from natural rockfall, so the events of the 1990's surprised me greatly. About all I can conclude after many decades in the Valley is that natural rockfall can happen anywhere there, and I'm unable to predict where or when with any degree of certainty.
Klutz-generated rockfall, on the other hand, is all-too-easy to predict!
John
Edit: Not only Muir, but Joseph LeConte, James Hutchinson, et al. documented trundling down the U-Notch. Since Greg's chart shows significantly less rockfall in the 1800's and early 1900's than now (Bias? What bias?), it naturally follows that trundling must have relieved pent-up pressure that resulted in more serious rockfall later. Thus, our inhibitionas on trundling now are clearly wrong-headed.
;-)
John
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Oplopanax
Mountain climber
The Deep Woods
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Nov 11, 2014 - 02:05pm PT
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Ow, right in the penstock!
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